The Combination of the R263K and T66I Resistance Substitutions in HIV-1 Integrase Is Incompatible with High-Level Viral Replication and the Development of High-Level Drug Resistance

Abstract

The R263K substitution in integrase has been selected in tissue culture with dolutegravir (DTG) and has been reported for several treatment-experienced individuals receiving DTG as part of salvage therapy. The R263K substitution seems to be incompatible with the presence of common resistance mutations associated with raltegravir (RAL), a different integrase strand transfer inhibitor (INSTI). T66I is a substitution that is common in individuals who have developed resistance against a different INSTI termed elvitegravir (EVG), but it is not known whether these two mutations might be compatible in the context of resistance against DTG or what impact the combination of these substitutions might have on resistance against INSTIs. E138K is a common secondary substitution observed with various primary resistance substitutions in RAL-and EVG-treated individuals. Viral infectivity, replicative capacity, and resistance against INSTIs were measured in cell-based assays. Strand transfer and 3= processing activities were measured biochemically. The combination of the R263K and T66I substitutions decreased HIV-1 infectivity, replicative capacity, and strand transfer activity. The addition of the E138K substitution partially compensated for these deficits and resulted in high levels of resistance against EVG but not against DTG or RAL. These findings suggest that the presence of the T66I substitution will not compromise the activity of DTG and may also help to prevent the additional generation of the R263K mutation. Our observations support the use of DTG in second-line therapy for individuals who experience treatment failure with EVG due to the T66I substitution. IMPORTANCEThe integrase strand transfer inhibitors (INSTIs) elvitegravir and dolutegravir are newly developed inhibitors against human immunodeficiency virus type 1 (HIV-1). HIV drug-resistant mutations in integrase that can arise in individuals treated with elvitegravir commonly include the T66I substitution, whereas R263K is a signature resistance substitution against dolutegravir. In order to determine how different combinations of integrase resistance mutations can influence the outcome of therapy, we report here the effects of the T66I, E138K, and R263K substitutions, alone and in combination, on viral replicative capacity and resistance to integrase inhibitors. Our results show that the addition of R263K to the T66I substitution diminishes viral replicative capacity and strand transfer activity while not compromising susceptibility to dolutegravir. This supports the use of dolutegravir in second-line therapy for patients failing elvitegravir therapy who harbor the T66I resistance substitution. R ecent strategies to treat HIV-1 infection involve the use of integrase strand transfer inhibitors (INSTIs), which are the most potent antiretroviral drugs (ARVs) to date and include raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG) (1). Despite this, the emergence of drug resistance mutations in integrase (IN) represents a concern for the future use ...

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“…While the latter had no effects on resistance to DTG, the addition of H51Y to R263K increased resistance to DTG to ϳ8-fold, while dramatically decreasing viral replication capacity by ϳ90% and enzyme strand transfer activity by ϳ80% (Mesplède et al 2013). Other studies have shown that R263K in combination with M50I, G118R, H51Y, E138K, T66I, N155H, or M184I/V slightly increased resistance to DTG but did not restore viral replication capacity (Quashie et al 2013aWares et al 2014;Anstett et al 2015;Liang et al 2015). Interestingly, no additional compensatory mutations have been identified for DTG, even in cell culture selection experiments conducted over more than 4 years (Wainberg and Han 2015).…”

Resistance to HIV Integrase Inhibitors: About R263K and E157Q Mutations

“…The study of Liang et al showed that the T66I substitution emerged from a wild-type virus but also from a R263K mutant and from a E138K-R263K double-mutant virus under RAL or EVG pressure [ 17 ]. The aim of this study was to assess the effects of the T66I and E138K substitutions, alone and in combination with R263K, on viral replicative capacity and resistance to INI.…”

Quantitative evaluation of the antiretroviral efficacy of dolutegravir

“…The second-generation HIV-1 integrase strand transfer inhibitor (InSTI) dolutegravir (DTG) has had dramatic clinical impact, demonstrating both efficacy (1-5) and a high barrier to resistance (6)(7)(8). Despite the remarkable success of DTG, its pharmacodynamic properties are incompletely understood.…”